116 GENUS— DICHELASPIS. 



Valves 5, generally appearing like 7, from each scutum 

 being divided into two distinct segments, united at the 

 rostral angle ; carina generally extending up between the 

 terga, terminating downwards in an imbedded disc, or 

 fork, or cup. 



Mandibles, with three or four teeth ; maxillae notched, 

 with the lower part of edge generally not prominent; 

 anterior ramus of the second cirrus not thicker than the 

 posterior ramus, not very thickly clothed with spines ; 

 caudal appendages uniarticulate, spinose. 



Distribution. — Eastern and Western warmer oceans in the Northern hemi- 

 sphere, attached to Crustacea, sea-snakes, &c. 



Description. — The capitulum appears to contain seven 

 valves ; but, on examination., it is found that two of the 

 valves on each side, are merely segments of the scutum • 

 these are united at the umbo, in three of the species, by a 

 narrow, non-calcified portion of valve, where the primordial 

 valve is situated ; in D. orthogonia^ however, the junction 

 of the two segments is perfectly calcified, and of the 

 same width as the whole of the basal segment. The 

 capitulum is much compressed, broad at the base, and 

 extends a little beneath the basal segments of the scuta. 

 The valves are very thin, often imperfectly calcified, and 

 generally covered with membrane. They are not placed 

 very close together, and in all the species a considerable 

 interspace is left between the carina and the two other 

 valves : in the D. Grayii the valves are so narrow that 

 they form merely a calcified border round the capitulum. 

 The membrane between the valves and over them, is 

 very thin, and is thickly studded, in some of the species, 

 with minute blunt conical points, apparently representing 

 spines. The valves in the same species present considerable 

 variations in shape ; in their manner or direction of growth, 

 and in the position of their primordial valves, they agree 

 with Lepas and Paecilasma. 



Scuta. — In three of the species the two segments, 



